ZnO-rGO nanocomposite based bioelectrode for sensitive and ultrafast detection of dopamine in human serum.

We present a tyrosinase-conjugated zinc oxide-reduced graphene oxide (Tyr/ZnO-rGO) nanocomposite system as a biosensing test-bed for rapid and sensitive detection of dopamine (DA). The bioelectrodes (Tyr/ZnO-rGO/ITO) were designed by covalently immobilizing tyrosinase enzyme on spin-coated films of ZnO-rGO nanocomposite prepared via self-assembly approach. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed fast electron transfer kinetics of ZnO-rGO/ITO electrode. The response studies of the Tyr/ZnO-rGO/ITO bioelectrode revealed ultrafast (0.34 ± 0.09 s) detection of DA in a wide linear dynamic range of 0.1-1500 pM. The significant performance of the biosensor in terms of low detection limit (8.75 ± 0.64 pM) and high sensitivity (39.56 ± 0.41 μA nM-1) values is attributed to the fast and unhindered electron transfer mechanism of ZnO-rGO matrix having low electrochemical band gap. The nanoplatform exhibited high selectivity toward DA in human sera, and remained stable up to 3 months at 4 °C, representing its suitability for clinical applications.